1) The spear shrinks so that the pipe completely covers it at some point.
2) The pipe shrinks so that the spear extends from both ends at some point.
3) Both shrink equally so the pipe just barely covers the spear at some point.
4) any of these, depending on the motion of the observer (moving with the spear, at rest
with the pipe, etc.)
An observer fixed to the pipe would measure the mass of the spear to be greater than
when at rest; an observer moving with the spear would measure the mass of the pipe to
be
5) more than when at rest.
6) less than when at rest.
7) the same as when at rest.
Answer:
The airspeed of an airplane is 100 km/h. When it is caught in a 100-km/h right-angled
crosswind, its speed across the ground below is about
1) 0 km/h.
2) 100 km/h.
3) 140 km/h.
4) 200 km/h.
5) more than 200 km/h.
If the airplane changes direction and flies at 60 degrees to the wind, its ground speed
will
6) decrease.
7) remain the same.